This invention relates generally to brazing, to oxidation resistant structures, to copper-brazed structures which are rendered oxidation resistant and to a method of diffusion alloying copper brazed joints and fillets, hereinafter referred to simply as "joints", and structures with aluminum. It is specifically concerned with providing oxidation resistant brazed joints in regenerator cores for turbine engines, although it is applicable to copper joints in similar matrix structures and to brazed copper joints generally.
Copper-brazed joints and fillets and related structures are alloyed according to the invention with aluminum for achieving oxidation resistance. A more direct method of copper-brazing with oxidation resistant copper-aluminum alloys, wherein the structure to be brazed is coated with a slurry of copper-aluminum, has proven to be undesirable because of poor "wetting." That is, the aluminum in the copper-aluminum alloy oxidizes and is not readily reduced by hydrogen. Consequently, the molten copper-aluminum alloy does not flow adequately to form suitable joints at the joint locations of the structure to be brazed.